Hard,sintered gold-colored alloy of tin cemented with ti,al,cr and fe alloy binder

ABSTRACT

A HARD, SINTERED GOLD-COLORED ALLOY ESPECIALLY USEFUL FOR COSTUME JEWELLRY AND ITEMS WHICH MUST WITHSTAND ACCIDENTAL ABRASION IS COMPOSED OF TIN AND AN ALLOY OF TI, AI, CR AND FE. THE SINTERED MATERIAL CAN BE GROUND AND POLISHED TO A HIGHER LUSTER AND IS EXTREMELY SCRATCHRESISTANT.

Int. Cl. czzc 29/00 US. Cl. 29--182.5 6 Claims ABSTRACT OF THE DISCLOSURE A hard, sintered goldcolored alloy especially useful for costume jewelry and items which must withstand accidental abrasion is composed of TiN and an alloy of Ti, Al, Cr and Fe. The sintered material can be ground and polished to a higher luster and is exremely scratchresistant.

BACKGROUND OF TI-IE INVENTION Where the appearance of gold such as in costume jewelry and in watches has been desired, it has been customary to use gold itself, whether solid or plated or in the form of a filling, a gold alloy, an alloy consisting of 90% Cu and 10% Al, or brass. However, the hardness of such materials lies in the range of Hv 150-250, so that they are easily scratched on contact with glass, concrete or hard metals such as iron and even by dust. As a result, it has been impossible to maintain a high polish and luster without frequent treatment.

Sintered alloys consisting of metallic carbides and binders such as Co, Ni and Fe have been used, but the appearance of such alloys is on the whitish side rather than golden. Attempts to use these same binders in combination with nitrides have been unsuccessful due to the fact that the nitrides are not readily wettable by these binders, and because at the necessary sintering temperatures, namely, between 1600 C. and 2000 C., the binders rise to the surface, leaving the nitrides unwetted. As a result, it has thus far been impossible to provide a Watchcase or costume jewelry having the appearance of gold which yet is of a material sufiiciently hard to withstand normal usage without losing its high polish and luster.

SUMMARY OF THE INVENTION Allows having the appearance of gold and having high hardness are produced by the use of TiN in the range of 70% to 97%, with the remainder being a binder consisting essentially of Ti, Al, Cr, and Fe.

Accordingly, it is an object of the present invention to provide an improved alloy, suitable for use in costume jewelry and watches, consisting of TiN with a binder including Ti.

Another object of the present invention is to provide an improved alloy for use in costume jewelry and watches, wherein said alloy is golden in color, corrosion-resistant and has high hardness and consists essentially of TiN with a binder containing Ti, Al, Cr and Fe.

Still other objects and advantages of the invention will in part be obvious and will in part be apparent from the specification.

United States Patent ice The invention accordingly, comprises a composition of matter possessing the characteristics, properties, and the relation of components which will be exemplified in the composition hereinafter described, and the scope of the invention will be indicated in the claims.

DESCRIPTION OF THE PREFERRED EMBODIMENTS TiN has a hardness of Hv 1950, a specific gravity of 5.44 g./ml., a melting point of 2950 C. and excellent corrosion-resistance. The appearance of the compound is somewhat similar to that of gold. The sintering temperature can be lowered substantially and the appearance of the material can be brought closer to that of gold by the use of Ti in combination with Al, Cr and Fe as a binder. The use of such a binder results in a substantial improvement in the sinterability and by adjustment of the quantity of binder and the composition thereof, the hardness and color tone can be adjusted as desired.

To produce articles in accordance with the present invention, powdered TiN together with the binder to be employed are weighed, and mixed for 24 hours in a wet ball-mill using ultra hard balls and a liquid such as benzene, at the end of which period the particles will have been reduced sufficiently in size. The resulting material is then dried in an inert gas such as nitrogen, a quantity of paraflin amounting to about 1% by weight of the material is added, and the material is pressed to produce a compact or preform. The pressure used during the production of the compact is about 4 tons/cm. Where test specimens are being made, a convenient size is 10 mm. in width, 30 mm. in length, and 6 mm. in thickness.

The compacts are heated gradually in a nonoxidizing atmosphere, such as nitrogen gas, until the paraffin is vaporized, after which the compacts are sintered for 60 minutes at a temperature lying between about 1620 C. and 1700 0., depending on the particular combination used. During the sintering, the pressure within the furnace is maintained at about 5X l0 mm. of Hg.

Following sintering and cooling, the compacts, whether specimens or articles, are polished 'by means of a diamond grindstone. Specimens may then be tested for mechanical properties such as hardness, strength and corrosion resistance, and for appearance factors such as surface condition and color tone. Corrosion resistance was tested by examinging the extent to which rust formed when the samples were soaked in 5% hydrochloric acid, in 7% nitric acid, and in 10% sulfuric acid, each test lasting for about 5 days. In all cases, it was found that the corrosion resistance was excellent, the strength and hardness proved to be satisfactory, and the appearance closely simulated that of gold.

Following are examples of the results achieved with compositions in accordance with the present invention:

Sintering condition, 1640" C.X60 min.

Specimens made in accordance with Example 1 proved to have a hardness of Hv 1080, a tensile strength of kg./mm. and an appearance closely simulating that of gold after polishing. They were completely resistant to the acid tests described above, and the luster proved to be lasting.

EXAMPLE 2 Sintering condition, 1660 C.X60 min.

A specimen prepared in accordance with Example 2 had a hardness of Hv 1120, a tensile strength of 103 kg./ mm. and a lustrous golden appearance subsequent to polishing with a diamond wheel. The corrosion resistance was excellent.

It was found that where the binder content ranges from 3 to 30% of the total weight of the alloy, sinterability. high hardness and tensile strength and excellent appearance are achieved. Also, resistance to corrosion is excellent. Where the binder content exceeds 30%, sinterability, tensile strength and color tone change to an extent such that the resultant alloy is unsatisfactory with respect to color and hardness. Similarly, if less than 3% of binder is incorporated, sinterability, hardness and color tone are also unsatisfactory.

For the most part, titanium is the principal component in the binder used, so that in the various compositions encompassed by the present invention, the titanium content may lie between 2.5 and 23 parts by weight where the total weight is 100 parts. Similarly, the total weight of aluminum, chromium and iorn is preferably between 1.33 and 10 parts by Weight where the total weight is 100 parts. Further, it has been found that Al, Cr and Fe are preferably but not necessarily in the ratio of 5:2:1 by weight. The quantity of binder used and the ratios of the components in the binder are varied in accordance with the color tone desired, and the hardness and tensile strength desired. Within the bounds set forth above, alloys having the appearance of gold when highly polished, having high hardness and high corrosion resistance have been achieved. These may be used in costume jewelry, for the manufacture of cigarette lighter cases and for use in watchcases, the last being a use in which particularly severe 4 conditions of abrasion and corrosion must be withstood.

It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the above composition of matter without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description shall be interpreted as illustrative and not in a limiting sense.

It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described, and all statements of the scope of the invention which, as a matter of language, might be said to fall therebetween.

What is claimed is:

1. A hard, sintered gold-colored alloy comprising 97 parts by weight of TiN and 3-30 parts by weight of a binder consisting essentially of Ti, Al, Cr and Fe.

2. The hard, sintered gold-colored alloy as defined in claim 1 wherein said Ti is present in from 2.5 to 23 parts by weight.

3. The hard, sintered gold-colored alloy as defined in claim 1 wherein said Al, Cr and Fe are present in the ratio of 5 22:1 parts by weight.

4. The hard, sintered gold-colored alloy as defined in claim 1 wherein said Al, Cr and Fe total from 1.33 to 10 parts by weight.

5. The hard, sintered gold-colored alloy as defined in claim 1, comprising 88 parts of TiN, 4 parts of Ti, 5 parts of Al, 2 parts of Cr, and 1 part of Fe by weight.

6. The hard, sintered gold-colored alloy as defined .in claim 1, comprising 88 parts of TiN, 10.67 parts of Ti, 0.83 parts of Al, 0.33 parts of Cr, and 0.17 parts of Fe, by weight.

References Cited UNITED STATES PATENTS 3,669,695 6/1972 Iler et a1 -205 3,514,271 5/1970 Yates 75205 3,507,631 4/1970 Yates 75205 CARL D. QUARFORTH, Primary Examiner B. HUNT, Assistant Examiner U.S. Cl. X.R. 75-205 

